|Ainsworth, Elizabeth - Lisa|
|Leakey, Andrew d|
Submitted to: Journal of Experimental Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/10/2006
Publication Date: 1/1/2007
Citation: Ainsworth, E.A., Rogers, A., Leakey, A.B., Heady, L.E., Gibon, Y., Stitt, M., Schurr, U. 2007. Does elevated atmospheric [CO2] alter diurnal C uptake and the balance of C and N metabolites in growing and fully expanded soybean leaves? Journal of Experimental Botany. 58(3):679-591. Interpretive Summary: Plants grown at elevated [CO2] typically have higher rates of photosynthesis (C uptake) and carbohydrate production. These increases could potentially feed increased leaf growth and expansion at elevated [CO2]. On the other hand, plant growth may be constrained by the ability to transport nutrients and carbon to growing organs and tissues. We investigated diagnostic markers of carbon and nitrogen metabolism in soybeans grown under field conditions at elevated [CO2]. Carbon and nitrogen metabolite pools were altered by growth at elevated [CO2] in both mature and growing soybean leaves. While carbohydrates were increased in mature leaves, they were not increased in young growing leaves, which implies that growth may have been carbon limited. Our results suggest adapting soybeans to allocate resources towards increased leaf area may be one strategy to improve plant performance in future environmental conditions.
Technical Abstract: Increases in growth at elevated [CO2] may be constrained by a plant’s ability to assimilate nutrients needed for new tissue in sufficient quantity to match the increase in carbon fixation and/or the ability to transport those nutrients and carbon in sufficient quantity to growing organs and tissues. Analysis of metabolites provides an indication of shifts in carbon and nitrogen partitioning due to rising atmospheric [CO2] and can help identify where bottlenecks in carbon utilization occur. In this study, we investigated the carbon and nitrogen balance in growing and fully expanded soybean leaves exposed to elevated [CO2] in a Free Air CO2 Enrichment (FACE) experiment. We measured diurnal photosynthesis and diurnal profiles of carbon and nitrogen metabolites during two different crop growth stages. Diurnal carbon gain was increased by ~20% in elevated [CO2] in fully expanded leaves, which led to significant increases in leaf hexose, sucrose and starch contents. However, there was no detectable difference in nitrogen-rich amino acids and ureides in mature leaves. In contrast to mature leaves, developing leaves had high concentrations of ureides and amino acids relative to low concentrations of carbohydrates. Developing leaves at elevated [CO2] had smaller pools of ureides compared to developing leaves at ambient [CO2], which suggests N assimilation in young leaves was improved by elevated [CO2]. This work shows that elevated [CO2] alters the balance of carbon and nitrogen pools in both mature and growing soybean leaves, which could have down-stream impacts on growth and productivity.